Cavity resonator structure for klystrons



vv smlmlml F. L. SALISBURY CAVITY RESONATOR STRUCTURE FOR KLYSTRONS Filed May 2, 1960 iiii l llllll July 9, 1963 mlm GF n tubes.

United States Patent O M 3,097,324 CAVI'IY RESONATOR STRUCTURE FR VKLYS'liRGNS Frederick L. Salisbury, Los Altos, Calif., assigner to Varian Associates, Palo Alto, Calif., a corporation of California Filed May 2, 1960, Ser. No. 26,249 8 Claims. (Cl. 3155.39)

This invention relates in geneial to high frequency electron'emissive devices and structural assembly thereof.

In electron discharge devices such as klystron tubes which have had a central body portion with an axial bore therein subdivided longitudinally by a plurality of cavity resonator partitions in the form of headers supporting drift tubes, the headers have been brazed at precise locations within the bore to provide specic gap spacings between the drift tubes supported by the headers. In the past, these headers were tightly held on shoulders within the bore of the tube prior to brazing, or in some instances spacers were provided in the gaps between adjacent drift In the latter case these spacers, of course, had to be removed from the tube after the brazing operationhad taken place. These prior art .assembly methods depended upon maintaining close tolenances in forming the bore and the headers so that the headers could be slideably positioned within the bore and held in axial alignment until the bnazing operation could be completed.

Furthermore, in tubes of this nature it is necessary to provide an :accurately aligned longitudinally positioned cathode 'assembly for producing the electron beam that is to pass through the tube. It is desirable that these cathodes be easily assembled and accurately adjusted for the desired cathode-anode spacing regardless of discrepancies in the size of other pants of the tube. In many previous tubes the entire cathode assembly was assembled in one openation whereby allowances for variations in the dimensions of the tube could not readily be made.

The object of the present invention is to provide a novel electron discharge device and structural assembly thereof whereby a rugged tube can be more easily and economically produced while keeping within close tolerances.

One feature of the present invention is the provision of a novel electron discharge device constructed from a bare minimum of separate :components assembled in a rugged unitary device capable of rneeting rigid requirements for reproducing specific electrical requirements in spite of mechanical variations in contain portions of the tube.

Another feature of the .present invention is the provision of la novel structural assembly of cavity resonator partitions within the bore of an electron discharge device wherein knurled circles or portions of circles are provided on the surface of the bore of the tube body member for positioning annular partitions therein.

Another feature of the present invention is the provision of a novel structural assembly of cavity resonator partitions within the bore of van electron discharge device wherein la knurl is provided on the surface of the bore adjacent substantially the middportion of the bore; a resonator partition is inserted in one end of the bore and xedly positioned on the knurl and then subsequent knurls iare successively provided, with partitions positioned thereon, from each end of the bore to form the desired number of cavity resonators.

v3,097,324 Patented July 9, 1963 Still :another feature of the present invention is the provision of a novel structural assembly of cavity resonator partitions within the bore of an electron discharge device wherein 4the bore is provided with a stepped diameter, the larger diameter step-s being located towards the ends of said bore; two knurls are provided on the step of smallest diameter and one knurl on each of the other steps, and resonator partitions of different diameters are slideably inserted Within the bore and onto the knurls on the surface thereof.

Other features and advantages of the present invention will become more apparent on la perusal of the following specication taken in connection with accompanying drawings wherein:

FIG. 1 is a longitudinal cross-section view, partially in elevation, of a klystron tube utilizing the features of the present invention,

FIG. 2 is yan enlarged side cross-section view of the stem-heater assembly andthe cathode-electrode assembly of the klystron .tube shown in FIG. 1 and showing in pliantom the manner in which these assemblies are put together,

rFlG. 3 is a side cross-section view of the main body portion of a klystron tube showing the novel manner in which the annular headers are positioned within the bore of the main body portion,

FIG. 4 is a side cross-section view of a portion of the body of an electron discharge device utilizing the features of the present invention, and

FIG. 5 is a side cross-section view of a portion of the body of another electron discharge device utilizing features of the present invention.

Referring now to FIGS. l through 3 of the drawing, a klystron tube utilizing yfeatures of the present invention in. cludes a central body portion l11 which is made from a unitary metallic block having la rnultidiameter longitudinal bore ,142 extending therethrough. A metallic hollow cylindrical drift tube 13 of a material with a relatively low coeicient of expansion such as steel and having circular resonator grids 1 4 and 15 on the ends thereof is positioned within the longitudinal bore 12 by an outwardly extending annular header `16. The walls of the drift tube 13 are parallel to the axis of the electron beam passing through the central body portion :11 of the tube. `Fixedly secured, as by brazing, within one end of the longitudinal bore 1,2 of the central |body portion 11 having an enlarged diameter is an annular anode structure 17 as of, for example, copper having a resonator grid .18 positioned in the aperture therethrough, and Within the other end of the centr-al body portion 11 is an annular header 19 .as of, for example, copper and with a resonator grid 20 positioned in the aperture therethrough. Within the cent-ral body portion 11, the annular anode structure 17 and the annular header `16 on the drift tube 13 serve as resonator partitions and define a re-entrant first cavity resonator 21; the header l16 on the drift tube 13 and the header 19 serve as resonator partitions and define a reentrant second cavity resonator `22. Pfhe header 16 on the drift tube 13 is provided with an aperture 23 therethrough for coupling the linst and second cavity resonators 21 and 22 together. A milled opening 24 in lthe side Wall of the central body portion l11 provides access to the second cavity resonator 22 for coupling oscillatory ener-gy out of the tube.

The drift tube 13 which is made yof a metal with a relatively low coefficient of expansion prevents the gaps between grids 14 and 18 and grids 15 and 20 from changing an appreciable amount when the klystron tube heats up.

The anode structure 17 and the headers 16 and 19 are positioned within the bore 12 of central body portion 11 by first providing raised portions such as knurls 25a, 25b and 25e respectively (see FIG. 3), encircling the Wall of the bore 12 of central body portion 11 at the positions at which these members are to be 'lxed. The surface surrounding the bore 12 of the centr-al body por- -tion 11 is then copper plated.' The annular header 16 which is of smaller diameter than that portion of the bore 12 at which the anode structure 17 is positioned is pressed into place on its knurl 2Sb through the anode end of the central body portion 11 clearing the knurl 25a. Then the anode structure 17 is pressed into place on its knurl `25a and the header 19 is pressed into position on its knurl 25e at the other end of the tube.

rings of brazinlg material positioned around the edges of the partitions at the time of insertion of the partitions into the body.

The raised portions may be provided by knurling or 'embossing the surface surrounding the bore 12 so long `as the surface is raised up into the bore such as a ridge or a series of ridges, a straight knurl or a diamond knurl, etc. Hereafter, in the specification and claims the word knurl will rbe used to indicate any such raised portion.

Although this method of `assembly is illustrated `as applied to a tube with only two cavity resonators it can be seen that this feature of the present invention can be used to assemble a tube with any number of cavity resonators (see FIG. 4). In a tube with, for example, live succesthe longitudinal bore 12, as by, for example, the use of sive cavity resonators A, B, C, D and E formed by successive resonator partitions a, b, c, d, e and f, the longitudinal bore is provided with a stepped diameter, the narrowest portion vof the surface sunrounding the bore being substantially midway thereof and `forming the circumferential wall for cavity resonators B, C and D. The diameter of the surface surrounding the bore is stepped outwardly in two places toward 4each end thereof to form the circumferential wall for cavity resonator A lat one end of the bore and cavity resonator E at :the opposite end of the bore. Knurls are provided at the .desired locations for the resonator partitions a, b, c, d, e and f, and then partitions a, b kand c are slideably inserted into their proper positions from one end of the bore and partitions d, e and are slideably inserted into their proper positions from the other end of the bore. Because of the stepped diameter of the bore each partition is of such a diameter as to clear all the knurls for larger diameter partitions. To facilitate construction of the tube equal steps in the diameter of the bore are used toward each end thereof, and these steps are provided at the desired location -for the inner edge of a partition so that cer-tain partitions are accurately positioned within the `bore by being pressed against the steps in the diameter of the bore.

Referring to FIG. 5 as an alternative embodiment of this present invention a tube with any number of cavity resonators can be .assembled by positioning cavity resonator partitions on knurls withi-n a bore of uniform diameter. Successive cavity resonators A B', C and D are formed along .the length of the bore by successive partitions a, b', c', d and e. A knurl is provided on the surtace Iof the 'bore adjacent the mid-portion thereof and the resonator partition c' is slideably inserted into one end of the bore and positioned on this knurl. The knurls `for walls b and d are then formed and associated walls b .an open-ended, cup-shaped heat shield 35.

and d then inserted thereon latter which two additional l knurls are formed and associated walls a and e' secured thereon. In this embodiment of the present invention the knurls could ybe properly spaced 'along the length of the bore by placing a Lguide extension on the end of the knurling tool so that each successive knurl will be made at a desired distance from an existing partition within the bore. l Obviously the two central-most partitions could be inl serted into the bore and onto knurls at the same time from opposite ends of the bore. It should be noted that the knurls lon the wall of the bore need not extend in a complete closed circle around the Ibore to perform their funcl tions but may, for example, include two or more segments of a circle.

Fixedly secured, as by brazing, Within an annular ange 26 on the end of the central body portion 11 Iadjacent the anode structure 17 is hollow cylinder 27 which supports l a beam generating assembly 28. 'In onder to assure proper alignment and spacing of the beam generating assembly 28, it is constructed from two sub-assemblies, a stemheater assembly 29 and la cathode-electrode assembly 31.

In the stem-heater assembly 29 an insulator disc 32 such as ceramic forms the end of the tube and is provided with lan annular projection 33 projecting axially into the tube and covered with a disc-shaped .sputter shield 34 which is dished to project into the space surrounded by the annu- Vend of the hollow cylinder 27. All the parts of this stemheater assembly 29 are held together in a jig and simultaneously brazed together in the 'brazing furnace.

Connecting tabs 39 are added connecting two of the leads 36 to the heat shield 35 thereby providing electrical connection to the cathode-electrode Iassembly 31 to be mounted on the stem-heater assembly 29. A spiral heater filament 40 projecting axially into the tube Within the heat shield 35 is then connected to the remaining lead 36.

The cathode-electrode assembly 31 includes cathode button 41 connected, as by spot welding, to an annular .flange on one end of Ia hollow heater housing support cylinder 42. The other end of the support cylinder 42 is :axially supported within a hollow cylindrical support sleeve 43 by means of an annular sleeve adapter 44. 'Ilhe support cylinder 42, the support sleeve 43 )and the sleeve adapter 44 are `held in a jig and *brazed together in a brazing furnace. An yopen-ended, cup-shaped focus electrode 45 with a stepped diameter tit-s within and is supported at the step in its `diameter on the forward end of the support sleeve 43.

The critical adjustments in the beam generating assembly 28 are axially positioning the cathode button 41 with respect to the central body portion 11 to form a beam that will pass through the entire tube and achieving the proper distance from the cathode button 41 to the anode structure 17 to properly form the beam and to pass as much of generating assembly 28` will be positioned axially with respect to the central body portion 11.

To position the cathode button `41 the proper distance from the anodestructure '17 before mounting the cathodeelectrode assembly 31 on the stem-heater assembly Z9, the distance betweenthe tip of the anode structure 17 and the annular flange-47 ion whichV the stem heater assembly will be supportedl is first measured. While mounting the cathode-electrode eassernby 31 onthe stem-heater assembly 29 these assembliesare moved axially with respectY to one another so that the difference between the distance from the forwardrnost portion of the stem-heater assembly support member 38 tothe cathode button 41 :and the iirst distance measured will provide the proper space between the cathode button 41 and the anode structure 17. Then, the heat shield 35 and the support sleeve 43 are xedly secured together, as by spot-welding, thereby connecting the stem-heater assembly and the cathode-electrode assembly 31. This connection can be more rigidly fixed, as by silver brazing, to make the tube more rugged.

As an additional feature in the beam generating assembly 28, as shown in phantom in FIG. 1 the support sleeve 43 can be divided into two portions insulated from one another by an insulator ring 48 such as alumina ceramic whereby the focus electrode 45 can be provided with a positive or negative bias w-ith respect to the cathode button 41 by means of an additional lead (not shown).

F or mass production of tubes utilizing the beam generating assembly illustrated here the stem-heater assembly 29 and the cathode-electrode assembly 31 for every tube could be connected together with a standard distance between -the forwardmost end of the stem assembly support member 38 and the cathode button 41. Then a spacer ring of selected thickness could be provided between the forwardmost portion of the stem assembly support member 38 and the annular flange 47 4on the hollow cylinder 27 -to compensate for variations in the distance between the annular flange 47 and the tip of the anode structure 17 on individual tubes.

A tab 49 is attached to the outside wall of the central body portion 11 for electrically grounding the tube body.

A collector `assembly 50` including an annular adapter 51 of non-magnetic material such as steel connected to one end of a hollow cylindrical collector 52 such as copper provided with radially outwardly extending cooling ns 53 is xedly secured to the end of the central body portion 11 adjacent the header 19 such as by a braze between the adapter 51 and the central body portion 11. An annular protective iin 54 of a hard material such as steel is xedly secured to the other end of the collector 52 to protect the other iins 53 from being bent out of shape due to rough handling of the tube. An exhaust tubulation 55 closes oif the outward extending end of the collector 52 and is provided therewithin with a milled baille 56 which provides gas access between the tube and the tip of the exhaust tubulation 55 but prevents direct bombardment of the tip of the tubulation 55 by electrons traveling axially down the tube. Since the annular adapter 51 is made of non-magnetic material the collector assembly 50 is magnetically shielded from the remainder of the tube to prevent focusing lof the electron beam within the collector assembly 50.

A waveguiding recess 57 is milled into the central body portion 11 surrounding the milled opening 24, and within this recess 57 a wave permeable window 58 such as alumina ceramic is supported in a cup-shaped window frame 59` vacuum-sealed to the external Isurface of the centr-al body portion 11 within the recess 57. A waveguide output flange `60 surrounds the recess 57 for coupling the tube to other microwave components.

Each of the cavity resonators 2.1 and 22 is tuned by an identical tuning assembly 62 contained in a tuner mounting block 63 supported on the side of the central body porti-on 11 opposite from the wave permeable window 58.

6. A milled opening 64 i`s provided -in the central body portion 11 into each cavity resonator,y and then both cavity resonators are sealed closed by la flexible tuner diaphragm 65 which is held between the central body portion 11 and the tuner mounting block 63. For each cavity resonator a cylindrical tuner rod 66 is slideably mounted within a cylindrical bore in the mounting block 63, one end of the tuner rod 66 being iixedly secured to the tuner diaphragm `65 for moving the tuner diaphragm in and out to tune the cavity resonator; Each tuner rod 66 is provided with a transverse slot 67 thereacross, and the mounting block 63 is provided with a large cylindrical aperture 68 communieating with the bore which houses the tuner rod 66, the axis of the aperture 68 being substantially perpendicular to the axis of the tuner rod 67 and providing access to the transverse slot 67 in the tuner rod 66. A tuner tool which slideably tits within the aperture 68 and is provided with an eccentric projection on the end thereof adapted to iit within the transverse slot 67 can be used to tune each cavity resonator whereby when the tuner tool is engaged in the aperture 68, rotation of the tool will move the tuner rods 66 in and out to tune the cavities. A set screw (not shown) is provided on the opposite side of the mounting block 63 from the aperture 68 for locking the tuner rod 66 when the cavity resonators have been properly tuned.

The construction of the central body portion with the cavity resonator partitions and the beam generating assembly and the methods of assembling these porti-ons of the tube would be equally applicable to electron discharge devices other than klystron tubes and utilizing a plurality of cavity resonators such as, for example, traveling wave tubes and linear accelerators using disc loaded waveguide.

Since many changes could be made in the above construction and many apparently widely ldiffe-rent embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. In an electron discharge device a central body portion including a longitudinal bore therethrough with knurls provided on the surface of the longitudinal bore at which cavity resonator partitions are to be located, and cavity resonator partitions positioned on the knurls within the longitudinal bore and ixedly secured to the central body portion.

2. The electron discharge device of claim l wherein the longitudinal bore of said central body portion is provided with a stepped diameter and knurls are provided on the surface of the steps at regions Where compartment partitions are to be located.

3. In an electron discharge device a central body portion including a longitudinal bore therethrough, said bore provided with at least a step in the diameter thereof adjacent one end thereof and knurls on the surface of said bore at which partition members are to be located, and partition members positioned on the knurls within the longitudinal bore, one of such partition members being positioned adjacent said step in the diameter of said bore.

4. In an electron discharge device a central body portion including a longitudinal bore therethrough, said bore provided with a plurality of steps in the diameter thereof, and knurls on the surface of said bore at which partition members are to be located, and partition members positioned on the knurls within the longitudinal bore, a partition member being positioned at least adjacent each of said steps in said bore.

5. In an electron discharge device a central body portion including a longitudinal bore therethrough, said body having spaced knurls located on the surface of the bore, caviity resonator partitions fixedly positioned on said knurls in said bore, adjoining cavity resonator partitions serving to define resonant cavities therebetween in said electron discharge device.

6. In an electron discharge device a centralV body portion including a longitudinal bore therethrough, said bore provided with a plurality of steps in the diameter thereof, said bore having spaced knurls located on the surface thereof, cavity resonator defining partitions xedly positioned on the spaced knurls in said bore, said adjoining partitions serving to define resonant cavities therebetween in said electron discharge device.

7. The device of claim 5 wherein more than two cavities are defined by said cavity resonator partitions.

8. 'I'he device of claim 6 wherein more than two cavities are defined by said cavity resonator partitions.

References Cited in the ile of this patent UNITED STATES PATENTS Levin May 24, 1960 

1. IN AN ELECTRON DISCHARGE DEVICE A CENTRAL BODY PORTION INCLUDING A LONGITUDINAL BORE THERETHROUGH WITH KNURLS PROVIDED ON THE SURFACE OF THE LONGITUDINAL BORE AT WHICH CAVITY RESONATOR PARTITIONS ARE TO BE LOCATED, AND CAVITY RESONATOR PARTITIONS POSITIONED ON THE KNURLS WITHIN THE LONGITUDINAL BORE AND FIXEDLY SECURED TO THE CENTRAL BODY PORTION. 